Thanks for the question.
There are several possibilities for the spots in the brain including;
1) Migraine headache related
2) Prior head injury related
3) Prior bran infection related (encephalitis, meningitis etc)
5) Chronic Ischemic small vessel diseases of the brain
6) MS (Multiple Sclerosis)
10) Idiopathic (cause is not found) etc
Not all these above may be applicable in your case; I am just discussing the various possibilities. Yours is most likely #10 in the above list (idiopathic type, and it not uncommon for these spots to be idiopathic in nature).
Below I have addressed each of these above mentioned possibilities;
Migraine related: These spots are not uncommonly found in patients with history of migraine headache (HA). Of course that is relevant in your case only if you have migraine type HA.
Head injury related (if you have this history)
Prior infection related (If you have this history)
Vasculitis: It is the inflammation of the arteries secondary to autoimmune type of disorders.
Chronic ischemic small vessel disease of the brain: It is seen in people who have chronic medical conditions like high blood pressure, diabetes, high cholesterol, triglycerides etc (applicable only if you have these risk factors).
MS (multiple sclerosis): The characteristic MRI appearance of the spots & your clinical manifestations will give a clue whether this could MS or not, although MS is bit less likely considering your cerebro spinal fluid x 3 was normal.
Leukodystrophies: These are seen mostly in children and extremely rare for your age.
CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts & Leuroencephalopathy): It is a hereditary disease where patients experience recurrent stroke or mini strokes.
MELAS (Mitochondrial Encephalopathy Lactic Acidosis Stroke like syndrome): This disease is caused abnormality in the mitochondria and patients present stroke or mini stroke like episodes.
Idiopathic: Sometimes in spite of an exhaustive work up you may not find any cause then the white matter diseases is called as idiopathic (cause is not found) - which appears to be the possibility in your case.
I know you already have seen neurologists and have been worked up. You may see them another time and go through with the above list and discuss with them your case again. They may also do another thorough neurological examination. Basically you are recommended to undergo a repeat thorough reevaluation from different perspectives including your detailed history, thorough clinical examination, meticulous & methodical interpretation of MRI finding (for the different possibilities of this type of MRI finding) etc and hopefully a final diagnosis may be arrived.
What I am trying to tell is the spots in the brain may be idiopathic, but it is advised to undergo a reevaluation to make sure nothing else is missed.
Please ask me if there are any further questions.